1. Field of the Invention
The present invention relates to a map data processing apparatus for updating map data using the most recent map data and a center system for transferring data to and from the map data processing apparatus.
2. Background Art
In a vehicle-installed navigation system operating with map data or the like, hitherto, map data has been stored in a record medium such as a CD-ROM and has been updated to new map data by replacing the medium of the CD-ROM.
In this manner, however, the map data is updated about once or twice a year and is not necessarily updated to the most recent map data.
To overcome this problem, a system of using communication means to update map data in a shorter cycle is proposed. (For example, refer to JP-A-11-95657, page 6, FIG. 4) JP-A-11-95657 discloses an example wherein the difference from full update of a map database (map DB) is generated as differential data in an information center and is sent from the information center to a vehicle, which then performs update processing, thereby updating the map data to most recent map data. The differential data generation time period is taken short, whereby new information can be provided for the vehicle in real time.
However, in the example in the related art, to enable even the user who purchases a vehicle-installed navigation system at timing between the timing at which one new version of software for the vehicle-installed navigation system is put on the market and the timing at which a new version or a revision version of the software is put on the market to update map data to the most recent map, for example, one year is divided into three time periods (time period 1 (first time period), time period 2 (next time period), and time period 3 (last time period)) so that differential data 1 is sent in time period 1, differential data 1 and differential data 2 are sent in time period 2, and differential data 1, differential data 2, and differential data 3 are sent in time period 3. The differential data amount increases with the time period and to update the map data to the most recent map, map storage means of a large memory capacity becomes necessary; this is a problem. There is also a problem of an increase in the communication cost because the amount of the data to be transmitted increases.
These topics will be discussed with specific numeric values of the data amounts. For example, when a vehicle-installed navigation system is purchased, the map database stored in a CD-ROM, etc., is about 600 MB. In contrast, assuming that the above-mentioned time period is one year, the differential data for each time period becomes about 500 KB and in the related-art example, the differential data amount increases with the time period in such a manner that the differential data amount becomes 500 KB in time period 1, becomes 1 MB in time period 2, and becomes 1.5 MB in time period 3; this is a problem.
This is represented in terms of versions as follows: In the system in the related-art example, accumulation to the corresponding time period is applied and the differential data from version 1.0 to version 1.1 may be transmitted in time period 1; in addition to the differential data from version 1.0 to version 1.1, the differential data from version 1.1 to version 1.2 needs to be transmitted in time period 2, and the differential data from the differential data from version 1.0 to version 1.1 to the differential data from version 1.m (m=n−1) to version 1.n needs to be transmitted in time period n.
Particularly, unlike map data used in GIS, etc., navigation map data is in a format having little or no room for data update (data addition, change, deletion, etc.,) for lessening the data size; although one data update from the original data is possible, it is substantially impossible to furthermore update the post-update data. In the system in the related-art example, update must be performed using the update data in all time periods from the original data.
For example, it is also possible to upgrade application software to a later version every time period in a personal computer (PC). In this example, of a plurality of programs making up the software, a previous program is replaced with an update program; this basically differs from the operation of rewriting a part of the old data to perform data update as in the related-art example. In software of PC, the differential data amount to the most recent data varies from one time period to another and therefore the data amount increasing in the future is unpredictable in advance.